ImmunoCAP - a truly quantitative allergy test

Having a quantitative IgE test result when investigating patients with suspected allergy opens up important new possibilities. Together with the medical history and a physical examination, you will be able to plan the best possible treatment. In some cases, you may even rule out allergy as the cause and thereby reducing worry and unecessary food avoidandance!

Value of quantitative results

The ImmunoCAP test results help identify the patient's baseline IgE antibody levels. Even allergens found at low levels that do not result in symptoms, should be followed. It also helps evaluate which allergens are the most important for causing symptoms and to follow changes in patient's IgE profile over time to:

  • predict and follow the disease development
  • reflect the effect of and compliance with avoidance/reduction
  • optimize medical strategies
  • evaluate tolerance development (food allergy, specific immunotherapy)
  • avoid unnecessary food challenges

Knowing a patient's specific IgE antibody levels for the substances to which they are sensitive increases the possibility of ranking how the different substances affect their symptoms.

More IgE – more symptoms

Based on thousands of test results, the generic curve above indicates what an allergen-specific IgE antibody value can mean in relation to symptoms. A general rule of thumb is that the higher the IgE antibody value, the greater the likelihood of symptoms appearing.

However, a person can have a low level of IgE antibodies and still have symptoms due to exposure to the allergen in question.

A final diagnosis should always be based on a combination of IgE test results, a physical examination and a patient’s clinical history.

The timing of symptoms is indivudual

Exactly when the symptoms against an allergy-causing substance will develop varies between individuals. The time-point depends on a number of factors, including:

  • The degree of exposure
  • The levels of IgE antibodies
  • The individual’s clinical reactivity

Factors to consider prior to diagnosis

Before making the final diagnosis, remember that several factors must be considered. Knowledge and understanding of the following topics will give a better overall picture of the patient’s situation.

Age

Children under two years of age may suffer from allergic disease although presenting with lower concentrations of allergen Specific IgE antibodies than older individuals.

Degree of atopy

Patients with a family history of allergy are at higher risk of developing allergy. The majority, however, of allergic children have non-allergic parents.

Allergen load

Take into account the total allergen sensitization, even if only one or a few allergens seem important at the time of the investigation. Different sensitizations may accumulate and it may be the least obvious that leads to symptom development. Multiple allergen sensitization indicates a higher risk of developing severe allergic disease.

Type of sensitizing allergen

Some allergens (e.g. peanut and tree-nuts) are considered to be particularly dangerous as they more often provoke severe symptoms such as anaphylaxis and asthma.

Previous symptoms

If the patient has experienced symptoms such as eczema, asthma and/or anaphylaxis in the past, even low IgE antibody levels must be considered.

Other triggering factors

Bacterial and viral infections as well as pollution frequently exacerbate symptoms in the allergic patient.

By adding the above considerations to an IgE antibody test result, combined with previous medical history and a physical examination, the allergy investigation can be fine-tuned to give a highly informative picture. The ImmunoCAP Specific IgE test result then forms a sound, scientific basis for a correct diagnosis, prognosis and follow-up of the allergic patient.

References

  • Söderström L et al. A further evaluation of the clinical use of Specific IgE antibody testing in allergic diseases. Allergy 2003;58:921-8
  • Sampson HA. Utility of food-specific IgE concentrations in predicting symptomatic food allergy. J Allergy Clin Immunol 2001;107:891-6

As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.